This retrospective study included 964 eyes from 500 subjects including 128 healthy normal eyes and 836 eyes with primary open angle glaucoma had various stages of visual field defects (572 early, 164 moderate and 100 severe). Both eyes of each patient were included in the study if they satisfied the entry criteria as follows: each eye had a best corrected visual acuity of 20/25 or better, a spherical equivalent refractive error between -5 and +5 diopters, clear ocular media with no clinically significant cataract, a normal open angle, and no previous intraocular surgical history.

The diagnosis of glaucoma was based on the presence of typical glaucomatous optic disc damage, as judged by stereoscopic examination by a glaucoma specialist (Y. J. Hong), and the presence of glaucomatous visual field loss as measured by SAP. The patients had no significant ocular diseases other than glaucoma and no other diseases affecting visual fields. The normal controls had no visual field changes on SAP, intraocular pressure below 21 mmHg, no optic nerve head or retinal nerve fiber layer changes suggestive of glaucoma, no other ocular disease or surgical history, no diabetes, and no family history of glaucoma.

All subjects were examined using SAP (Carl Zeiss Meditec Inc, Dublin, CA) with a 30-2 Swedish interactive threshold algorithm (SITA) standard strategy. The minimal visual field abnormality was determined by SAP and was defined as significant when: (1) the Glaucoma Heimifield Test was "outside normal limits" in 2 consecutive fields; (2) 3 or more adjacent points were present in an expected location of the central 24-degree field that depressed below the 5% level on the pattern deviation plot (PDP), one of which must have been below the 1% level in 2 consecutive fields; or (3) pattern standard deviation (PSD) was significant below the 5% level in 2 consecutive tests.10 Visual field defects were divided into 3 stages: early, moderate, and severe.11 The early stage of a glaucomatous visual field defect was defined as having: (1) a mean deviation (MD) of no worse than -6dB, (2) fewer than 25% of the points depressed below the 5% level and fewer than 15% of points depressed below the 1% level on PDP, and (3) no point within the central 5-degree field with a sensitivity of less than 15dB. A moderate stage of visual field defect was defined as having: (1) MD of worse than -6 dB but no worse than -12dB, (2) fewer than 50% of the points depressed below the 5% level and fewer than 25% of points depressed below the 1% level on PDP, (3) no point within the central 5-degree field with a sensitivity of less than or equal to 0 dB, and (4) only 1 hemifield containing a point with sensitivity less than 15dB within 5 degrees of fixation. Criteria for severe defects in glaucoma were defined as: (1) MD worse than -12 dB, (2) more than 50% of the points depressed below the 5% level and more than 25% of points depressed below the 1% level on PDP, (3) any point within the central 5-degree field with a sensitivity of less than or equal to 0 dB, and (4) both hemifields containing a point(s) with sensitivity less than 15 dB within 5 degrees of fixation.

The RNFL photographs were recorded with blue reflectance ("red-free") images using the HRA1. Two of authors (S. Hong & S. J. Ha) interpreted the RNFL photos using the two scoring systems (Table 1) under the masking of the diagnosis. For darkness scores, the contrast and brightness of RNFL photos were adjusted to distinguish sharply the retinal blood vessels from the background using Heidelberg Eye Explorer program (Heidelberg Engineering, Dossenheim, Germany). On location scores were shown in Fig . 1. A reference plane was set across the horizontal raphe dividing the papillomacular bundle into two vertical halves. RNFL in the 15 degrees above and below this reference plane was termed the 'Temporal' sector. RNFL in the 75 degrees from the end of the 'Temporal' sector to the vertical line dividing the optic nerve head into two halves was termed as 'Supero-, and Infero- temporal' sectors for the respective vertical positions. The remaining 180 degrees of nasal RNFL was designated as the 'Nasal' sector. In cases with a large or multiple RNFL defect over several sectors, the highest location score was applied.

If the two scores did not agree with each other, the other two glaucoma specialists (Y. J. Hong & G. J. Seong) were asked to interpret it. Table 1 showed the scoring methods to assess the RNFL photo.9 The RNFL defect score I was a summation of each score, and the RNFL defect score II was the product of each score - RNFL defect, darkness, width, and location. The RNFL defect score I could range from 0 to 11, and the RNFL defect score II could range from 0 to 54. The interval between the SAP and RNFL photography was less than 1 month.

To assess correlations between RNFL photographs using HRA1 and SAP, we compared two RNFL defect scores (RNFL defect score I and II) and visual field indices (MD and PSD) of SAP. Statistical comparisons between groups were conducted using an independent 2-tailed Student t-test, and P-values less than 0.05 were considered statistically significant. Statistical analysis for linear regression was performed using the MedCalc for Windows program, version 7.6.0.0 (MedCalc Software, Mariakerke, Belgium). Statistical analyses other than linear regression were carried out using the program SPSS for Windows, version 11.5 (SPSS Inc, Chicago, IL).